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1.1 DK Shield (Muddy soil pressure) method
The DK shield method was developed from 1974 in order to stabilize and excavate the cutting face of the soil with high water content and/or soft ground. The outline of the method is as follows. (Ref. Figure-2)
The cutting face shall be balanced and supported by the muddy soil itself.
The spoke type of cutter instead of the full face cutter is equipped basically.
Muddy soil is produced in the chamber by mixing with additive agent and excavated soil by the cutter with mixing blade.
Controlling the jack and the muddy soil pressure (B & D in Fig-2) by soil pressure gage make a balance with the existing ground pressure and ground water pressure (A & C in Fig-2).
Figure-2 DK shield tunnel boring system
Excavation shall proceed while adjusting the speed of boring and the volume of muck discharge, so that the muddy soil pressure balances with the existing ground pressure and ground water pressure.
In the case of failing to achieve the above balance, displacement at the ground surface may occur.
Excavated soil can be disposed of, after being hardened by simple method.
From the above points, DK shield tunneling method can be applied for various types of excavation and different kinds of soil, and can also applied for the condition of very deep underground excavations and high water pressures.

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